Our Research in Focus
Spermatozoa have been traditionally viewed as vehicles for the delivery of only the paternal genome to oocytes upon fertilization. In this context, paternal contributions to offspring phenotype are strictly limited to germline genetic information without the ability to impart environmental information that is encountered during the life course. However, a growing body of compelling data from our lab (and others) demonstrates that environmental exposures can be embodied within the developing male germ cell without altering the germline genetic information and, in turn, can affect pregnancy success and offspring phenotype.
Paternal environmental contributions to reproductive health via sperm epigenetics
The Pilsner lab addresses the interface of environmental epidemiology, toxicology, and reproductive health with a particular emphasis on epigenetic mechanisms. Specifically, our research provides a paternal perspective by delineating the role of sperm epigenetics as a pathway linking paternal preconception environmental exposures to reproductive and offspring health. Such research is critical to understand the paternal environmental determinants of reproductive health and early-life development. We also recognize that translational research extends from bench-to-bedside, and our current research portfolio echoes this notion with research spanning traditional silos that include both epidemiologic and rodent research. The centerpiece of our research is the environmental health preconception cohort, Sperm Environmental Epigenetics and Development Study (SEEDS), in which we are examining the relationships of preconception phthalates in males on embryo development and live birth. To complement our research goals in humans, we are also conducting experimental studies in mice to better understand the intergenerational inheritance of the sperm methylome stemming from preconception phthalate exposures. Collectively, the impact of our research aims to facilitate a paradigm shift in the way reproductive success is viewed, such that the burden of environmental health may not be restricted to expectant mothers but rather is equally shared with male partners via sperm epigenetics.
Uncovering novel biomarkers of male infertility and reproductive success
The second arm of research in the Pilsner lab aims to identify novel sperm biomarkers of male infertility and couples’ reproductive success. Male factor infertility is typically determined using measures of semen quality and World Health Organization (WHO) cut points to define abnormality. However, a wealth of data demonstrate that this approach poorly predicts reproductive success and semen parameters have minimal association with fecundability, raising questions about the significance and interpretation of conventional approaches for measuring male infertility. Our research in SEEDS demonstrate that sperm mitochondrial DNA copy number (mtDNAcn) is a strong predictor of semen parameters (sperm count, concentration, motility, and morphology) and is also related to fertilization rates. To expand this line of research, findings in the LIFE Study show that sperm mtDNAcn is strongly related to couples fecundability as measured by time-to-pregnancy.
Aging of the male germ line and sperm epigenetics
Chronological age is a significant determinant of human fecundity and fertility. The disease burden of infertility is likely to continue to rise as parental age at the time of conception has been steadily increasing, especially in developed countries. While the emphasis has been on the effects of advanced maternal age on adverse reproductive and offspring health, new evidence suggests that, irrespective of maternal age, higher male age contributes to longer time-to-conception, poor pregnancy outcomes as well as adverse health of the offspring in later life. However, chronological age does not capture the internal (e.g., genetics) and external factors (e.g., environmental conditions) that may affect cellular aging processes. Therefore, chronological age is a proxy measure of the actual biological age of cells. As such, research in the Pilsner lab is also examining the effect of aging on sperm epigenetics. Our research has shown that chronological age has a profound effect on sperm DNA methylation and that we can leverage this strong relationship to build epigenetic clocks to estimate the biological age of male germ cells.
Windows of susceptibility during male germ cell development
In humans, male germs cells do not attain reproductive capacity until the second decade of life. Despite this long latency period, male germ cells begin development early in fetal life and, upon sex determination, embark on a remarkable journey of cellular differentiation and morphological changes to prepare for its sole purpose—the propagation of its genome. During development, male germ cells progress from primordial germ cells (PGCs) to diploid spermatogonia and then finally to haploid spermatozoa. To undergo these transformations, stage-specific epigenetic reprogramming is required - each of these reprogramming events (Steps 1-5) represent windows of susceptibility in which environmental exposures can sculpt the epigenetic landscape of sperm prior to fertilization. The Pilsner lab is currently examining the effects of environmental exposures on the preconception window (Steps 3-5) of male germ cell development known as spermatogenesis, which takes around 74 days (around 35 days in mice) to produce mature haploid spermatozoa from diploid spermatogonia. Thus, epigenetic reprogramming during spermatogenesis in the adult provides a final opportunity for sperm to “epigenetically match” their current environment prior to fertilization.
If you are interested in reading our publications on these topics, see them here.
Funding
Current funding
2024-2029 NIH/NICHD: R01HD105792
Sperm mitochondrial biomarkers and male reproductive health.
Role: Principal Investigator
2023-2029 NIH/Office of the Director: UG3OD023285
Prenatal Exposures and Child Health Outcomes 2: Increasing ECHO Urban and Rural Diversity
Role: Co-Investigator
2017-2022 NIH/NIEHS: R01-ES028214
Male preconception phthalates and offspring embryo and sperm allele-specific methylome programming
Role: Principal Investigator
2018-2023 NIH/NIEHS: R01-ES028298
Paternal preconception phthalates and reproductive health - potential mediation through sperm DNA methylation.
Role: Principal Investigator
2019-2022 NIH/NIEHS: R01-ES030942
Paternal preconception exposure to phthalates impacts sperm function, the epigenome, fertility and reproductive outcomes in mice and men.
Role: Principal Investigator
Past funding
2016-2018 NIH/NIEHS: R21-ES026778
Embryonic inheritance of sperm methylome after adult exposure to phthalates
Role: Multi-Principal Investigators with Jesse Mager
2014-2017 NIH/NIEHS: 1K22-ES023085-01
Phthalate Exposure, Sperm DNA Methylation and Early-life Development
Role: Principal Investigator
2013-2016 NIH/NCI: R15-CA170111-01
Epigenotyping in Peripheral Blood DNA and Risk of Breast Cancer
Role: Co-Investigator (Principal Investigator: Susan Sturgeon)
2014-2016 Russian Science Foundation: 14-045-00065
Effects of persistent organic pollutants and endocrine disrupting chemicals on male fertility and epigenetic reprogramming of male germ cells.
Role: Co-investigator/Scientific advisor (Principal Investigator: Oleg Sergeyev)